Function mesh draw wired surface. You can use meshnum for changing number of lines to be drawn.
MGL code:
call 'prepare2d' title 'Mesh plot':rotate 50 60:box:mesh a
C++ code:
void smgl_mesh(mglGraph *gr) { mglData a; mgls_prepare2d(&a); if(big!=3) gr->Title("Mesh plot"); gr->Rotate(50,60); gr->Box(); gr->Mesh(a); }